1. Field of the Invention
The present invention relates to a pneumatically-driven equipment, and, more specifically, to an efficiency valve in that equipment.
2. Description of the Related Art
Pneumatically driven equipment typically relies on mechanically moving parts to operate. The equipment will typically split the inlet motive air into process air and control air, in which the process air is used to perform the work and the control air is used to control the direction or motion of the mechanical components.
However, there is an inherent inefficiency that occurs in such air-driven equipment. The inefficiency is related to the reaction time or response time of the mechanical components as compared to the flow rate of both the process air and control air. In other words, the flow rate of the motive air far exceeds the velocity of the mechanical components because of friction losses and other dynamic losses acting on the mechanical components, created by the movement of the mechanical components. The inefficiency occurs when motive air is wasted by allowing it to continuously flow un-restricted into the pneumatic equipment when the process air has completed a first segment of work and the control air is mechanically moving components to a position that allows the process air to perform a second segment of work.
An example of this inefficiency is illustrated in FIGS. 1-3, which depict a schematic representation of an air-operated piston pump having a general design. In FIG. 1, inlet motive air is split into process air and control air. Control air positions the directional valve piston 11 inside directional valve 10 by filling chambers 12. Control air is also channeled out of chamber 12 and directional valve 10 and into pilot valve 40, and is then directed through pilot valve piston 41 to be channeled back to directional valve 10, thereby pressurizing chamber 13 in directional valve 10. Although the control pressure is equal for both chambers 12 and 13, the surface area of piston 11 on which the control pressure is acting is greater in chamber 13, causing piston 11 to move and remain to the “left” in directional valve 10. This allows the process air to pass through directional valve 10 and directional valve piston 11 and then be channeled to pump unit 30, thereby expanding into air chamber 32, acting on piston 31, and moving piston 31 to discharge liquid from liquid chamber 33. At the same time, movement of piston 31 toward the right pulls shaft 54, thereby moving piston 21 inside pump unit 20. Movement of piston 21 toward the other pump unit causes liquid to be drawn into liquid chamber 23 as once-used process air is released from air chamber 22 out of pump unit 20 and channeled through directional valve 10 and directional valve piston 11 to atmosphere.
In FIG. 2, piston 21 engages and moves shaft 64, which is connected to pilot valve piston 41 inside of pilot valve 40. Movement of piston 21 moves shaft 64 and pilot valve piston 41 to a position that allows channeled control air to be released to atmosphere from chamber 13 inside directional valve 10. Control air pressure in chamber 12 acts on directional valve piston 11, moving directional valve piston 11 toward the right inside directional valve 10.
In FIG. 3, directional valve piston 11 in directional valve 10 is held stationary by the control air pressure in chamber 12 acting on directional valve piston 11, thereby allowing process air to be channeled through directional valve 10 and directional valve piston 11 to pump unit 20, where it expands into air chamber 22 as once used process air is released from air chamber 32 in pump unit 30. The process air is further channeled through directional valve 10 and directional valve piston 11 to atmosphere, making pistons 21 and 31 and shaft 54 reverse their previous directions, thereby causing piston 21 to force liquid from liquid chamber 23 to discharge as piston 31 draws liquid into liquid chamber 33.
The inefficiency with the above-described design occurs during the transition from FIG. 2 to FIG. 3. During the total time period that it takes moving pilot valve piston 41 in pilot valve 40 to move to a position that re-directs control air to or from directional valve 10 and directional valve piston 11 moves completely to its new position to allow process air to perform a new segment of work (from “left” in FIG. 2 to “right” in FIG. 3), process air is allowed to continue entering the air chamber (air chamber 32 in FIG. 2) unrestricted, which overfills or over pressurizes the air chamber without additional liquid being discharged from it corresponding liquid chamber (liquid chamber 33 in FIG. 2). This overfilling or over pressurizing of the air chamber is a waste of energy.
There is, therefore, a continued need for pneumatically driven equipment such as air-driven liquid pumps that are more efficient and utilize less energy than previous designs.